aco: improve code sequences for 16bit packing

This includes using alignbyte for GFX6 and GFX7,
and 32-bit instructions for GFX8.

Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7189>
2 files changed